This application claims priority benefits under 35 USC xc2xa7119 of Japanese Patent Application Serial No. 11-146154, filed on May 26, 1999, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to method of and apparatus for producing a coated body by using ion plating, in each of which coating material particles ionized in a vacuum container coat and adhere to the surfaces of a body to be coated.
2. Description of Related Art
As examples of a method of coating a substrate surface with metal or other substance, there are known a vacuum evaporation method, an ion plating method, a sputtering method, a plasma method and the like, in each of which a coating substance is gasified or ionized in a vacuum, causing the substance thus ionized to come into collision with the substrate surface.
These methods are used for coating a variety of accessories and electronic parts and are applied even for particle bodies having particle sizes in a range, for example, from several microns to several mm. Particle bodies having sizes on the order of microns are called fine powder. According to the present invention, however, fine powder and granules are generally referred to as particle bodies.
For example, when only a half face of a particle body comprising glass is coated with titanium or the like, the particle body is increased in brightness by light refracted inside of the glass in addition to light reflected from the coated portion, thus producing an article excellent in decoration properties.
When the sputtering above-mentioned is used for such coating, the following troubles are caused. Because the sputtering speed is low, the target is required to be increased in size or in number in order to improve the film forming ability. Further, the target usage efficiency is low.
When a CVD (chemical vapor deposition) is used, expensive gas can disadvantageously be utilized only on the order of several % in view of film forming efficiency, and it is indispensable to install facilities for collecting a highly reactive gas in order to assure safety. This not only makes the facilities in a large scale, but also increases the installation cost.
On the other hand, according to an ion plating method of prior art, a subject to be coated is disposed above the evaporation source. Accordingly, when the subject to be coated is fine particle bodies, it is very difficult to merely hold, above the evaporation source, a number of particle bodies with their undersides facing the evaporation face.
When it is supposed that the evaporation source is disposed above the subject to be coated, the following troubles are newly caused. At an evaporation face comprising the bottom of the evaporation source, a coating substance is liquefied after heated and molten, and then evaporated. However, the liquefied coating substance is readily converted into drops due to its surface tension. This increases the contact angle of the drop surface of the coating substance with respect to the evaporation face, causing the liquefied coating substance to readily drop on the particle bodies. This disadvantageously prevents a uniform thin film from being formed on the surfaces of the particle bodies.
It is an object of the present invention to provide a making method of a coated body by using ion plating and a making apparatus of the same, each of which is high in coating speed and is capable of forming a uniform thin film.
To achieve the object above-mentioned, the present invention provides, as a preferred embodiment, a making method of a coated body by using ion plating, comprising: a step of heating a melt and evaporating source housed in an evaporation container disposed above a subject to be coated in a vacuum container; a step of evaporating the melt and evaporating source in the form of evaporated particles through a number of fine evaporation holes formed in an evaporation face formed by the bottom of the evaporation container, yet preventing the melt and evaporating source from dropping down; a step of ionizing the evaporated particles obtained from the melt and evaporating source with the use of plasma generated between the evaporation container and the subject to be coated; and a step of coating, from above, the surface of the subject to be coated with the ionized evaporated-particles, causing the ionized evaporated-particles to adhere to the surface of the subject to be coated, thus forming a coating film thereon.
In the ion plating method of ionizing a substance to form a thin film, the embodiment above-mentioned is arranged such that ions of the thin-film forming material are caused to gravitationally fall such that the ions coat and adhere to, from above, the surface of the subject to be coated. Accordingly, a uniform coating film high in adhering intensity can be formed in a short period of time. Further, the evaporation holes are very fine. This prevents the melt and evaporating source from dropping through the evaporation holes, thus enabling a uniform coating film to be formed.